Sealing apparatus for gas turbine

ABSTRACT

A seal ring (1) securing inner shroud members (32) of stationary blades (31) is provided with arm portions (2, 3) projecting along lower surfaces of end portions of the inner shroud members (32). Honeycomb seals (4a, 4b) are mounted on the arm portions (2, 3), respectively. The honeycomb seal (4a) is disposed opposite fins (11a) provided on a rotor arm portion (11) of a platform (22) of a moving blade (21) so that a predetermined clearance (t) can be maintained between the honeycomb seal and the fins. On the other hand, the honeycomb seal (4b) is disposed opposite fins (14b) provided on a seal portion (14a) of a sealing plate (14) of the moving blade (21) so that a predetermined clearance (t) can be maintained between the honeycomb seal and the fins. The inner shroud members (32) undergo deformation after operation of the gas turbine. However, because the honeycomb seals (4a, 4b) are mounted on the arm portions (3, 2), respectively, of the seal ring (1) disposed separately and independently from the inner shroud members (32), the honeycomb seals (4a, 4b) can remain unaffected by the deformation of the inner shroud members (32), whereby the predetermined clearances (t) can be consistently maintained.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a sealing apparatus for a gas turbineand more particularly relates to a sealing apparatus for a gas turbinein which clearance variations in a sealing structure intervening betweenthe inner shroud members of stationary blades and the platforms ofmoving blades are eliminated to improve sealing performance.

2. Description of the Related Art

FIG. 5 is a sectional view showing conventional sealing structureportions in a gas turbine. In the figure, reference numeral 21 denotes amoving blade, 22 denotes a platform thereof, 23 denotes a sealing plate,and numeral 24 denotes a blade root portion. A plurality of movingblades 21 are mounted radially around a rotor by way of the respectiveroot portions 24. Reference numeral 31 denotes a stationary bladedisposed adjacent to the moving blade 21, and numeral 32 denotes aninner shroud member of the stationary blade 31. Reference numeral 33denotes a cavity defined inside of the inner shroud member, and numeral34 denotes an annular shaped seal ring. Reference numeral 35 denotes anair hole provided in the seal ring 34 through which the cavity 33 and aspace intervening between the stationary blade 31 and the blade rootportion 24 of the adjacent moving blade 21 are communicated with eachother. Reference numeral 36 denotes a sealing portion provided in theseal ring 34, wherein a labyrinth seal or the like is adopted to sealthe rotatable root portion 24.

Reference numeral 37 denotes a honeycomb seal mounted on the innershroud member at the upstream side thereof as viewed in the direction ofthe combustion gas flow, numeral 38 denotes a honeycomb seal alsomounted on the inner shroud member 32 at the downstream side thereof.These honeycomb seals 37 and 38 are disposed in the vicinity of rotorarm portions 25a and 25b of the platforms 22 of the adjacent movingblades 21, respectively, and provide resistance to air leaks to therebyprovide sealing.

This sealing structure will be described in more detail. FIG. 6 shows aportion D in FIG. 5 in detail. The honeycomb seal 38 having a largenumber of honeycomb cores is disposed at an end portion of the innershroud member 32 in such a state that the open side of the honeycomb ispositioned closely to a tip end portion of the rotor arm portion 25a ofthe platform 22. Moreover, a clearance t between the honeycomb seal 38and the rotor arm portion 25a is substantially 1 mm.

In the above mentioned sealing structure, the air 40 leaking at a highpressure from the cavity 33 (see arrows) flows out into a low-pressurecombustion gas passage from a space defined between a side wall of theseal ring 34 provided at the stationary blade 31 and the sealing plate23 of the moving blade 21 by way of the clearance t formed between thehoneycomb seal 38 and the rotor arm portion 25a at the downstream sideof the combustion gas flow. As the high pressure leaking air 40 flowsalong the path mentioned above, resistance to its flow increases.Consequently, a sealing effect takes place between the honeycomb seal 38and the rotor arm portion 25a which are disposed close to each other,whereby the high temperature combustion gas is prevented from enteringthe interior of the stationary blade 31. Similarly, the leaking airflows out into a space between the honeycomb seal 37, provided at thestationary blade 31 and disposed at the upstream side of the combustiongas flow, and the rotor arm portion 25b, resulting in increasedresistance to the flow of leaking air, whereby sealing is provided forthe combustion gas passage.

However, the conventional sealing structure for the gas turbinedescribed above suffers a problem in that since the honeycomb seals 37and 38 are mounted directly at the end portions of the inner shroudmembers 32 of the stationary blades 31, nonuniform variation occurs inthe clearance t with respect to the circumferential dimension thereofdue to deformation of the inner shroud members 32 after operation of thegas turbine, dimensional dispersion of the inner shroud members uponmanufacturing or due to other causes. Furthermore, because the rotor armportions 25a and 25b of the platform 22 which rotate relative to theinner shroud members 32 are each of an annular shape and follow acircular path upon rotation, the clearances t formed between thehoneycomb seals 38 and 37 mounted on the inner shroud members 32 and therotor arm portions 25a and 25b of the platform 22 can not be controlledat all, thus giving rise to a problem.

The situation mentioned above will be explained with reference to thedrawings. FIG. 7 is a sectional view taken along the line E--E in FIG.6. Referring to the figure, a plurality of inner shroud members 32 ofthe stationary blades 31 are mounted independent of one another in anannular array at an appropriate distance along a circumference, and arespaced from the circular rotor arm portion 25a by a predetermineddistance. Moreover, the honeycomb seal 38 is mounted on the inner shroudmember 32, and the space between the honeycomb seal 38 and the rotor armportion 25a represents the clearance t. The state of the inner shroudmembers 32 immediately after the manufacturing thereof is indicated bysolid lines. After operation of the gas turbine, the inner shroudmembers 32 and the stationary blades 31 undergo deformation due torotation of the rotor arm portion 25a, as indicated by the broken lines.This deformation causes the honeycomb seal 38 to deviate from itsdesired position, which in turn brings about variation in the clearancebetween the honeycomb seal 38 and the rotor arm portion 25a.Accordingly, control of the clearance between the honeycomb seals 38mounted on the inner shroud members 32 and the rotor arm portion 25a ofthe platform 22 is made impossible.

OBJECT OF THE INVENTION

In order to solve the problems mentioned above, it is a primary objectof the present invention to provide a sealing apparatus for a gasturbine in which the mounting portion for the honeycomb seal is alteredso that even when the inner shroud member undergoes deformation afteroperation of the gas turbine, the clearance between the honeycomb sealand the arm portion of the platform can be protected against variation,to thereby make it possible to control the clearance of the sealingportion.

Further, it is another object of the invention to provide a sealingapparatus of a structure which can further enhance the sealingperformance without being effected by the deformation of the innershroud member such as mentioned above.

SUMMARY OF THE INVENTION

To achieve the objects mentioned above, the present invention providesthe following apparatus.

(1) A sealing apparatus for a gas turbine according to the presentinvention is characterized in that it includes arm portions projectingfrom a seal ring for fixedly securing inner shroud members of stationaryblades, said arm portions extending along front end portions and rearend portions, respectively, of the inner shroud members as viewed in anaxial direction thereof, and sealing members mounted on the armportions, to constitute sealing mechanisms through cooperation with endportions of platforms of moving blades disposed adjacent to the frontend portion and the rear end portion, respectively, of the inner shroudmember, to thereby seal off the interior of the inner shroud membersfrom a combustion gas passage. Moreover, a honeycomb seal shouldpreferably be employed as the sealing member.

With the arrangement of the present invention described in the aboveparagraph (1) in which the sealing members are mounted on both armportions of the seal ring, respectively, the sealing members can becompletely protected against the influence of deformation of the innershroud members even when the individual inner shroud members undergodeformation, accompanied by positional deviation of the inner shroudmembers, because the arm portions of the seal ring are each an annularshape constructed independent from the inner shroud members.Consequently, the sealing members mounted on the arm portions of theseal ring can not be effected by the deformation of the inner shroudmembers. Hence the clearances formed between the sealing members and theend portions of the platform of the moving blade can be maintained at apredetermined dimension. Accordingly, a clearance set at an optimaldimension can be maintained even after operation of the gas turbinebegins. Thus, clearance control can be significantly enhanced whencompared with the conventional sealing structure.

In other words, with the arrangement according to the present inventiondescribed in the paragraph (1), the clearance at the sealing portion canbe set at an optimal dimensional value because the clearance can beprotected against variation.

(2) The sealing apparatus for a gas turbine according to the presentinvention with the structure set forth in the above paragraph (1) isfurther characterized in that each of the end portions of theaforementioned platform of the aforementioned moving blade is providedwith a projection disposed opposite the aforementioned sealing member.

By virtue of the arrangement according to the present inventionmentioned in the above paragraph (2) in which the projection is providedat each end portion of the platform of the moving blade so as to beopposite each sealing member, the setting of the clearance can befacilitated. Further, by providing a large number of fins at eachprojection, the resistance to the flow of leaking air can be furtherincreased, thus making it possible to decrease the amount of leakingair. Consequently, the performance of the gas turbine can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectional schematic view showing a sealingapparatus for a gas turbine according to an embodiment of the presentinvention, i.e., a mode for carrying out the invention.

FIG. 2 is an enlarged sectional view of a portion A in FIG. 1 showingdetails of a sealing structure between a platform of a moving blade andan inner shroud member of a stationary blade on a downstream side of acombustion gas flow.

FIG. 3 is a sectional view taken along the line C--C in FIG. 2 showingthe relationship between honeycomb seals provided in association withthe inner shroud members, respectively, and a rotor arm portion of asealing plate of a moving blade.

FIG. 4 is an enlarged sectional view of a portion B in FIG. 1 showing,in detail, a sealing structure between the platform of a moving bladeand an inner shroud member of a stationary blade on the upstream side ofthe inner shroud member as viewed in the direction of combustion gasflow.

FIG. 5 is a schematic view showing a conventional sealing structure in agas turbine.

FIG. 6 is an enlarged sectional view of a portion D in FIG. 5 showing,in detail, a sealing structure between the platform of a moving bladeand an inner shroud member of a stationary blade on the downstream sideof the inner shroud member as viewed in the direction of the combustiongas flow.

FIG. 7 is a sectional view taken along the line E--E in FIG. 6 showingthe relationship between a honeycomb seal provided in association withthe inner shroud and a rotor arm portion provided in association withthe platform.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail in conjunction withwhat are presently considered preferred embodiments thereof withreference to the accompanying drawings.

In the following description, like reference numerals designate like orcorresponding parts throughout the drawings. Also in the followingdescription, it is to be understood that terms such as "right", "left","upper", "lower" and the like are words of convenience and are not to beconstrued as limiting terms.

FIG. 1 is a schematic view showing a sealing apparatus for a gas turbineaccording to an embodiment of the present invention, i.e., a mode forcarrying out the invention. In the figure, reference numeral 21 denotesa moving blade, 22 denotes a platform thereof, and numeral 24 denotes ablade root portion. Reference numerals 11 and 12 denote rotor armportions disposed, respectively, at the front and rear ends of theplatform 22 as viewed in the axial direction, wherein the rotor armportion 11 disposed on the upstream side of combustion gas flow isdisposed at an inner position when compared with that of theconventional turbine, while the rotor arm portion 12 disposed on thedownstream side is disposed at an outer position when compared with thatof the conventional turbine. Reference numerals 13 and 14 denote sealingplates covering a shank portion, wherein the sealing plate 14 isprovided with an integral arm portion 14a having fins 14b.

Reference numeral 31 denotes a stationary blade, 32 denotes an innershroud member thereof, 33 denotes a cavity formed inside of the innershroud member 32, and numeral 34 denotes a sealing portion. A labyrinthseal and the like is adopted a the sealing portion 34, which is disposedclose to and opposite the blade root portion 24 of the adjacentrotatable moving blade 21. Reference numeral 35 denotes an air holethrough which the cavity 33 and the space around the adjacent movingblade 21 are communicated with each other.

Reference numeral 1 denotes a seal ring of an annular shape which isprovided with an arm portion 2 at the upstream side of the combustiongas flow. The arm portion 2 is disposed close to the end portion of theinner shroud member 32 and extends along a curved surface of the endportion, wherein a honeycomb seal 4b is mounted on a lower surface ofthe arm portion 2. Similarly, an arm portion 3 is disposed at thedownstream side of the combustion gas flow direction of the seal ring 1.This arm portion 3 is disposed so as to extend along the end portion ofthe inner shroud member 32, and a honeycomb seal 4a serving as thesealing member is mounted on the lower surface of the arm portion 3.

FIG. 2 is a detailed view of a portion A in FIG. 1 and shows thedownstream side of the inner shroud member 32 of the stationary blade31. Referring to the figure, the seal ring 1 is mounted on the innershroud members 32. The seal ring 1 is formed in an annular shape anddivided into two parts. Each seal ring 1 has the arm portion 3 and aprojection 5 at the side adjacent to the moving blade 21 and is fixedlysecured to the inner shroud members 32 by means of bolts 6.

The arm portion 3 projects toward the platform 22 and extends along theinner curved surface of the end portion of the inner shroud member 32,and the honeycomb seal 4a is mounted on the lower surface of the armportion. A large number of downward opening honeycomb cores are disposedin the honeycomb seal 4a, and the rotor arm portion 11 of the platform22 of the moving blade 21 is disposed opposite open surface of thehoneycomb seal. A large number of fins 11a are disposed on the uppersurface of the rotor arm portion 11 with a predetermined clearance t,e.g. 1 mm, relative to the honeycomb seal 4a. The sealing plate 13 ofthe moving blade 21 is provided with an arm 13a projecting toward theseal ring 1 to form a seal in cooperation with a projection 5 providedin association with the stationary blade 31.

FIG. 3 is a sectional view taken along the line C--C in FIG. 2. As canbe seen in the figure, the annular arm portion 3 of the seal ring 1 isdisposed at the inner side of a plurality of stationary blades 31 andthe inner shrouds thereof which are independently disposed in a circulararray, and the circular arm portion 3 is disposed so as to extend alongthe inner surfaces of the inner shroud members 32. The honeycomb seal 4ais mounted on the lower surface of the annular shaped arm portion 3continuously in an annular form. Moreover, since the honeycomb seal 4ais bulky, it is mounted on the arm portion 3 being divided into twoparts in the circumferential direction.

In FIG. 3, the inner shroud members 32 in the state before the gasturbine is put into operation are depicted by solid lines. At this time,the inner shroud members 32 are disposed at respective predeterminedpositions circumferentially. On the other hand, after operation of thegas turbine begins, the inner shroud members are deformed at everystationary blade, as indicated by broken lines. However, since thehoneycomb seal 4a is mounted on the arm portion 3 of the seal ring 1which is disposed separately and independently from the inner shroudmembers 32, as described previously, the honeycomb seal can remainunaffected by the deformation of the inner shroud members 32, and theclearance t between the honeycomb seal 4a and the fins 11a mounted onthe rotor arm portion 11 of the platform 22, as shown in FIG. 2, can bemaintained at a predetermined distance.

FIG. 4 is a detailed view of a portion B in FIG. 1 and shows the innershroud members 32 of the stationary blade 31 at the upstream side of thecombustion gas flow. The seal ring 1 mounted at the inner side of theend portions of the inner shroud members 32 has a projecting arm portion2 formed by bending the seal ring 1 approximately in an L-like shapealong the curved surfaces of the inner shroud members, and the honeycombseal 4b is mounted on the lower surface of the seal ring with the opensurface of the honeycomb seal facing downward. On the other hand, theabove mentioned sealing plate 14 is mounted on the platform 22 of themoving blade 21, and the sealing portion 14a of the sealing plate 14projects to a position opposite the arm portion 2 which is provided inassociation with the inner shroud member 32. Fins 14b are provided onthe sealing portion 14a and are disposed opposite the honeycomb seal 4bwith a predetermined clearance t being maintained relative to thehoneycomb seal 4b.

Since the honeycomb seal 4b is also mounted on the arm portion 2 of theseal ring 1 disposed separately and independently from the inner shroudmembers 32, as described hereinbefore in conjunction with therelationship between the inner shroud members 32 and the honeycomb seal4a mounted on the arm portion 3 with reference to FIG. 3, the honeycombseal can remain unaffected by the deformation of the inner shroudmembers 32. Thereby, the clearance t intervening between the honeycombseal 4b and the fins 14b of the sealing plate 14 mounted on the platform22, as shown in FIG. 4, can be maintained at a predetermined distance.

In the sealing structure described above, the high pressure leaking air40 flows out from the cavity 33 into the low-pressure combustion gaspassage through the space formed between the side wall of the seal ring1 of the stationary blade 31 and the sealing plate 13 of the movingblade 21 by way of the clearance t formed between the honeycomb seal 4aand the fins 11a of the rotor arm portion 11 at the downstream side ofthe inner shroud member 32 of the stationary blade 31 of the gas flow(see FIG. 2). As the high pressure leaking air 40 flows along the pathmentioned above, resistance to its flow increases. Consequently, asealing effect is brought about between the honeycomb seal 4a and thefins 11a disposed adjacent to each other, whereby the high temperaturecombustion gas is prevented from entering the interior of the stationaryblade 31. Similarly, the leaking air flows out through the space definedbetween the honeycomb seal 4b and the fins 14b of the sealing plate 14at the downstream side of the moving blade 21, whereby sealing isprovided for the combustion gas passage due to the increased resistanceto the flow of leaking air.

In the sealing apparatus according to the instant embodiment of theinvention which operates as described above, the inner shroud members 32of the stationary blades 31 are deformed at every stationary blade afteroperation of the gas turbine begins, as indicated by broken lines inFIG. 3. However, since the honeycomb seals 4a and 4b are mounted on thearm portions 2 and 3 of the annular shaped seal ring 1 which is splitinto two parts and provided separately and independently from the innershroud members 32, deformation of the individual inner shroud members 32or dispersion with respect to the mounting dimensions and the like exertno influence on the honeycomb seals 4a and 4b of the seal ring 1.Consequently, the sealing clearances t defined between the honeycombseals 4a and 4b and the fins 11a and 14b, respectively, can bemaintained at predetermined dimensions.

As is apparent from the foregoing, according to the invention of theinstant embodiment, the clearances t which are defined, respectively,between the honeycomb seals 4a and 4b and the fins 11a and 14b providedin association with the moving blade 21 and which are set at optimumdimensions upon design for manufacturing and assembling of the gasturbine can be maintained at the predetermined dimensions,notwithstanding deformation of the inner shroud members 32 afteroperation of the gas turbine begins. In other words, clearance controlcan be realized. In contrast, when the honeycomb seal is directlymounted on the inner shroud member 32, the clearance mentioned abovechanges due to the deformation of the inner shroud member 32 afteroperation of the gas turbine begins. This problem can be solved with thestructure according to the instant embodiment of the invention, wherebyclearance control for the seal can be remarkably improved.

Furthermore, because the above mentioned clearances are accurately set,the resistance to the flow of leaking air can be further increased bydisposing the plurality of projecting fins 11a and 14b in associationwith the moving blade 21 opposite the honeycomb seals 4a and 4b. Since,the amount of leaking air can be decreased, the operating performance ofthe gas turbine can be enhanced.

Moreover, the arm portion 2 of the seal ring 1 shown in FIG. 4 may beconstituted by split members to ensure ease of assembly. Of course, itgoes without saying that the seal ring 1 can be formed as an integralstructure including the arm portions 2 and 3.

Also, the fins provided in association with the moving blade 21 may bemounted directly on the rotor arm portion 11 which is integral with theplatform 22 or, alternatively, mounted on the sealing plate 13 or 14provided separately and independently from the platform 22.

Furthermore, in the structure according to the instant embodiment of theinvention, the arm portions 2 and 3 provided in association with theinner shroud members 32 of the stationary blades 31 are disposed at anouter side, while the sealing portion 14a and the rotor arm portion 11aprovided in association with the moving blades 21 are disposed at aninner side. Accordingly, the honeycomb seals 4a and 4b provided inassociation with the stationary blade 31 face inward while the fins 14band 11a provided in association with the moving blade 21 face outward,and hence are disposed opposite each other. Consequently, it is equallypossible to dispose the arm portions 2 and 3 provided in associationwith the inner shroud members 32 of the stationary blades 31 at theinner side while each of the sealing portions 14a and the rotor armportion 11a provided in association with the moving blades 21 isdisposed at an outer side. Accordingly, the honeycomb seals 4a and 4bprovided in association with the stationary blades 31 face outward whilethe fins 14b and 11a provided in association with the moving blades 21face inward, and hence are disposed opposite each other.

In the foregoing, the embodiments of the present invention which areconsidered preferable at present and other alternative embodiments havebeen described in detail with reference to the drawings. It should,however, be noted that the present invention is never restricted tothese embodiments but other various applications and modifications ofthe sealing apparatus for the gas turbine can be easily conceived andrealized by those skilled in the art without departing from the spiritand scope of the present invention.

What is claimed is:
 1. A sealing apparatus for a gas turbine, comprisingarm portions projecting from a seal ring, respectively, said seal ringfixedly securing inner shroud members of stationary blades, said armportions extending along front end portions and rear end portions ofsaid inner shroud members, respectively, as viewed in an axial directionthereof, wherein said seal ring, which is provided with said armportions, is constructed separately and independently from said innershroud members, and sealing members mounted on said arm portions,respectively, to constitute sealing mechanisms through cooperation withend portions of platforms of moving blades disposed adjacent to saidfront end portion and said rear end portion, respectively, of said innershroud member, wherein said sealing mechanism seals off an interior ofsaid inner shroud members from a combustion gas passage.
 2. A sealingapparatus for a gas turbine as set forth in claim 1, wherein saidsealing member is a honeycomb seal.
 3. A sealing apparatus for a gasturbine as set forth in claim 1, wherein a projection is disposedopposite said sealing member at each of the end portions of saidplatform of said moving blade.
 4. A sealing apparatus for a gas turbineas set forth in claim 1, wherein each of said arm portions disposed inassociation with said seal ring is formed integrally with said sealring.
 5. A sealing apparatus for a gas turbine as set forth in claim 1,wherein each of said arm portions disposed in association with said sealring is formed separately and independently from said seal ring.
 6. Asealing apparatus for a gas turbine as set forth in claim 1, whereinsealing portions are disposed separately from the end portions of saidplatform of said adjacent moving blade, and wherein said sealingmechanisms are realized, respectively, through cooperation of saidsealing portions and said sealing members mounted on said arm portions,respectively.
 7. A sealing apparatus for a gas turbine as set forth inclaim 6, wherein each of said sealing portions provided in associationwith said moving blade is provided with a projection disposed oppositeto said sealing member.